Asphalt roads and other asphalt surfaces typically include a base road, formed from a compacted aggregated material, such as limestone, crushed concrete, or similar aggregates, and an asphalt binder disposed on the base road. The aggregated material transmits load from the surface of the road to the base, withstands the abrasive wear of traffic, and provides a non-skid surface. The asphalt binder holds the aggregated material together, preventing loss and displacement of material, and forms a waterproof seal for preventing water from entering or leaving the base road. Additionally, the asphalt binder serves to bond the first course of surface treatment to the base, to strengthen the top 0.05 to 2 inches of the base, to protect the base prior to application of materials to the surface, to create a workable platform on the base, and to help control debris due to dust.
Conventional asphalt binders, also referred to as prime coats, typically include one or more cutback asphalts, which combine liquid and solid asphalts with a variety of volatile organic compounds, hydrocarbons, and other solvents. A typical cutback asphalt contains primarily volatile organic solvents of varying grades, possibly mixed with a small amount of water or other additives, used to thin a mixture of asphalt and other hydrocarbons. Volatile organic solvents are environmentally unfriendly, can evaporate over time, causing extensive air pollution, and can wash from the surface of a road in the form of run-off, causing water pollution.
Cutback asphalts must be heated prior to application, increasing the time required to prepare and apply the prime coat while creating safety concerns related to handling the heated material. Often, application of cutback asphalts requires heating beyond the flash point of many of the materials, creating significant risk of fire. Further, after application, cutback asphalts require a significant amount of time to cure before a coated base road can be subjected to construction traffic. Due the significant quantity of hydrocarbons and other solvents that are present in cutback asphalts, a great deal of time is required for these volatile components to evaporate, before the base is dry and properly cured. After curing, excess cutback asphalt applied to a base road must be blotted and cleaned to prevent evaporation or run-off. Additionally, the solvents in cutback asphalts can be potentially unsafe for construction personnel to handle without taking cumbersome precautions, and can be potentially unsafe for individuals who reside close to a site where cutback asphalts are in use.
Due to the environmental damages and human liability inherent when using cutback asphalts, use of cutback asphalts has become increasingly subject to environmental regulations. In many states, use of cutback asphalts is restricted to unpopulated and minimally populated areas, such as sections of roadways between cities, while alternatives to cutback asphalt must be used within and proximate to populated areas.
As a safer and less environmentally damaging alternative to cutback asphalts, emulsified asphalts have been developed, which contain smaller quantities of volatile organic compounds than cutback asphalts, do not require heating to apply, and cure more quickly than cutback asphalts. However, emulsified asphalts exhibit reduced effectiveness compared to cutback asphalts, primarily due to their high water content, among other factors. Use of asphalt emulsions often results in an improper cure for a base road and insufficient penetration into the base road. Additionally, while asphalt emulsions are considerably safer and less environmentally damaging than cutback asphalts, asphalt emulsions still contain a significant quantity of volatile organic compounds.
A need exists for an asphalt prime coat that contains a significantly lower quantity of hydrocarbon-related volatile organic compounds than other existing alternatives, including both cutback asphalts and emulsified asphalts, thereby substantially reducing or eliminating environmental concerns and human liability when applying or handling the materials, or when residing in proximity to a site where the asphalt prime coat is in use.
A further need exists for an environmentally friendly asphalt prime coat that overcomes the limited functionality of conventional emulsified asphalts, such as by penetrating from 0.5 inches to 2 inches, or more, into a base road, while retaining the benefits of emulsified asphalts, including a rapid curing time and the ability to be applied without requiring heat or blotting of excess material.
A need also exists for an asphalt prime coat that can fully evaporate within twenty-four hours of application. Oil based prime coats, including asphalt emulsions, typically require three to seven days for evaporation. A prime coat that dries within a twenty-four hour lapse of its first application could generate significant cost savings for a general contractor or asphalt paving contractor.
The present embodiments meet these needs.